1. Field of the Invention
The invention relates to an apparatus for generating high-power or output, high-voltage pulses, particularly for TE gas lasers, having at least one charge unit, and a pulse-generating network connected on the input side to the at least one charge unit and on the output side to the laser electrodes, a first branch and a second branch connected parallel to one another to the laser electrodes, the first branch having a first charge capacitor of relatively high capacitance and a magnetic switch connected in series therewith in the form of a saturatable inductor, and the second branch having a second charge capacitor, the second charge capacitor having a lower capacitance than the first charge capacitor, at least one high-voltage switch serving as a trigger for initiating a saturation of the magnetic switch and the discharge of the first charge capacitor into the laser electrode path, through the saturable magnetic switch.
In the prior art, voltages across the laser electrodes of up to 50 KV, depending on the electrode spacing and pressure, are needed to operate transversely excited (TE) excimer lasers. The voltage increase at the laser electrodes is tripped by a suitable switching operation in a so-called pulse generating network. The duration of the voltage increase is on the order of magnitude of from several tens of nanoseconds up to a hundred nanoseconds. The switch being used must have a high holding voltage, must be capable of switching high peak currents, and must have a long service life. It is only for low switching energies that the hydrogen-filled thyratrons typically used as switches meet these requirements. With increasing energy, thyratrons can no longer handle the high peak currents and yet still have an adequate service life.
Major efforts have therefore been devoted to relieving thyratrons or replacing them with other types of switches. For instance, circuits have been proposed that have a combination of magnetic switches as a passive switch element, and a spark gap as an active switch. For example, reference is made to an article entitled "High Efficiency XeCl Laser with Spiker and Magnetic Isolation" by C. H. Fisher et al, Applied Physics Letters 48 (23), Jun. 9, 1986, pp. 1574-1576. FIG. 1 shows a basic circuit diagram. Information on the basic operation of magnetic switches can be found in the literature, for instance in a publication entitled "Magnetic Switches and Circuits" by W. C. Nunnally, Los Alamos National Laboratory Report, LA-88 62 MS, published in September 1981. Only the function of the circuit will be explained herein.
A disadvantage of such circuitry is the high voltage occurring at the switch element at the spark gap, which makes it impossible to use economical thyratrons under some circumstances. Moreover, if a pulsed capacitor charging is used, one additional switch element is needed. In such a circuit, the switch element (at a spark gap or a thyratron, for instance) is not grounded, so that the voltage supply of the circuit (trigger voltage or heating voltage, for instance) is likewise exposed to the high voltages to be switched.
It is accordingly an object of the invention to provide an apparatus and method for generating high-power, high-voltage pulses, particularly for TE gas lasers, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type, and in other words in which the voltage and current load of the high-voltage switch in the trigger branch can be reduced without having to make sacrifices in terms of the efficiency of the laser discharge.